Case 9

Published on 02/03/2015 by admin

Filed under Internal Medicine

Last modified 22/04/2025

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 1725 times

[level-membership-for-internal-medicine-category]

Case 9

A 56-year-old woman with diabetes and a family history of coronary artery disease (CAD) was referred for exercise SPECT MPI for evaluation of exertional chest pain. The resting ECG was normal.

She exercised for 9:20 on a Bruce protocol, achieving an estimated workload of 10 METs. The peak heart rate was 144 beats/min (88% of maximum age-predicted heart rate). She described severe (9/10) chest pain at peak exercise, and there was greater than 1 mm ST depression at peak exercise. The blood pressure response was normal.

SPECT Images

image

The SPECT images demonstrate a severe and extensive, partially reversible perfusion defect involving the anterior, anteroseptal, apical, and inferoapical regions. The perfusion pattern suggests proximal left anterior descending (LAD) disease.

In addition, the left ventricular cavity appears larger on poststress images compared to resting images. This finding (sometimes termed transient ischemic dilatation) is suggestive of extensive ischemia and is a marker of increased risk for future cardiac events. Note that the increased stress/rest LV cavity ratio (SRLVCR) is apparent on the vertical and horizontal long-axis images. Be wary of commenting on increased SRLVCR if the finding is only visually evident on the short-axis images. Misalignment of the short-axis slices may result in artifactual elevated SRLVCR. Misalignment of the long-axis slices will result in apparent increased SRLVCR on only half of the slices, while the reverse (decreased SRLVCR) will be evident on the other half of the slices.

Polar Map

image

When the tracer distribution is compared to a female-specific normal database, there is an extensive (46% of the left ventricle), partially reversible (26% of the defect) perfusion defect in the anterior, anteroseptal, apical, and inferoapical regions. The partial (rather than complete) defect reversibility is suggestive of infarction with residual (“border zone”) inducible ischemia.

Viability Polar Map

image

Using a 50% reduction in resting regional 99mTc-sestamibi activity as an arbitrary threshold for myocardial viability, the resting tracer distribution suggests that a significant portion of the defect zone is composed of infarcted (nonviable) myocardium.

Poststress Gated SPECT Images

image

The poststress gated SPECT images demonstrate severely reduced regional systolic thickening in the anterior, anteroseptal, apical, and inferoapical regions, with moderately reduced global left ventricular systolic function (LVEF = 39%). The computed left ventricular volumes are mildly increased (left ventricular end-diastolic and end-systolic volumes = 160 and 99 mL, respectively). Reduced regional systolic thickening on poststress images can be caused by infarction, postischemic myocardial stunning, or an artifactual underestimation of wall thickening due to a severe perfusion defect.

Coronary Angiography

• LVEF = 55% normal wall motion
• LAD: 95% proximal PCI (DES)
• LCX: 10% diffuse
• RCA: 10% diffuse

As expected, coronary angiography demonstrated severe (95%) stenosis of the proximal left anterior descending (LAD) coronary artery. The stenosis was treated with a drug-eluting stent.

Interestingly, the left ventriculogram demonstrated normal myocardial systolic thickening in all regions with a normal left ventricular ejection fraction (55%). This suggests that the severely reduced regional systolic thickening on poststress gated SPECT images was not due to infarction. The reduced regional systolic thickening on gated SPECT could represent postischemic myocardial stunning or an artifactual underestimation of wall thickening by the gated SPECT algorithm caused by the severe perfusion defect.

Myocardial Stunning or Imaging Artifact?

image

Using only a single poststress gated SPECT acquisition, it is not possible to distinguish postischemic myocardial stunning from an artifactual underestimation of wall thickening by the gated SPECT algorithm. If myocardial stunning is responsible, the regional systolic dysfunction would be expected to resolve over time, and improvement would be detected on serial poststress gated SPECT acquisitions. If an artifactual underestimation of wall thickening by the gated SPECT algorithm is responsible, the regional dysfunction would be expected to persist over time (because the perfusion defect responsible for the artifact would persist).

Clinical Follow-Up

The patient returned 8 months later for follow-up exercise 99mTc sestamibi SPECT MPI. She denied chest pain since the PCI.

She exercised for 10:50 minutes on a Bruce protocol (13.1 METs). Peak heart rate was 154 beats/min (94% of maximal age-predicted heart rate). No exercise-induced symptoms were reported, and the blood pressure and ECG responses were normal.

SPECT Images 8 Months Later

image

The SPECT images demonstrate normal homogeneous myocardial perfusion in all regions. Inducible ischemia is no longer present in the territory of the left anterior descending coronary artery (LAD). The previously noted resting perfusion defect (suggestive of infarction, based on resting defect zone tracer activity < 50% of maximal tracer activity) is no longer present.

The stress/rest LV cavity ratio is now normal (0.82).

Gated SPECT Images 8 Months Later

image

The gated images demonstrate normal myocardial systolic thickening in all regions, with normal global left ventricular systolic function (LVEF = 53%). The computed left ventricular volumes are normal (left ventricular end-diastolic and end-systolic volumes = 99 and 47 mL, respectively).

Comparison of Resting SPECT Images at Baseline and 8 Months After PCI

image

There is a marked change in the resting SPECT perfusion images following PCI of the LAD. Homogeneous myocardial perfusion is now present, and the left ventricular cavity size is smaller. In retrospect, the severe resting perfusion abnormality (on the initial baseline study) was entirely due to ischemia. No infarction is evident on follow-up imaging.

Teaching Point

Be cautious in diagnosing infarction in the presence of severe inducible ischemia, even if incomplete defect reversibility is present and regional myocardial systolic thickening is reduced. It is more appropriate to emphasize ischemia on the report. The presence (and extent) of infarction can be overestimated in the setting of severe ischemia.

[/level-membership-for-internal-medicine-category][not-level-membership-for-internal-medicine-category]

Case 9

A 56-year-old woman with diabetes and a family history of coronary artery disease (CAD) was referred for exercise SPECT MPI for evaluation of exertional chest pain. The resting ECG was normal.

She exercised for 9:20 on a Bruce protocol, achieving an estimated workload of 10 METs. The peak heart rate was 144 beats/min (88% of maximum age-predicted heart rate). She described severe (9/10) chest pain at peak exercise, and there was greater than 1 mm ST depression at peak exercise. The blood pressure response was normal.

SPECT Images

image

The SPECT images demonstrate a severe and extensive, partially reversible perfusion defect involving the anterior, anteroseptal, apical, and inferoapical regions. The perfusion pattern suggests proximal left anterior descending (LAD) disease.

In addition, the left ventricular cavity appears larger on poststress images compared to resting images. This finding (sometimes termed transient ischemic dilatation) is suggestive of extensive ischemia and is a marker of increased risk for future cardiac events. Note that the increased stress/rest LV cavity ratio (SRLVCR) is apparent on the vertical and horizontal long-axis images. Be wary of commenting on increased SRLVCR if the finding is only visually evident on the short-axis images. Misalignment of the short-axis slices may result in artifactual elevated SRLVCR. Misalignment of the long-axis slices will result in apparent increased SRLVCR on only half of the slices, while the reverse (decreased SRLVCR) will be evident on the other half of the slices.

Polar Map

image

When the tracer distribution is compared to a female-specific normal database, there is an extensive (46% of the left ventricle), partially reversible (26% of the defect) perfusion defect in the anterior, anteroseptal, apical, and inferoapical regions. The partial (rather than complete) defect reversibility is suggestive of infarction with residual (“border zone”) inducible ischemia.

Viability Polar Map

image

Using a 50% reduction in resting regional 99m

[/not-level-membership-for-internal-medicine-category]